PIR sensor pIC16f877 explanation pLEASE!!

#include <16F877A.H>
#device ADC=10
#fuses HS, NOWDT, NOPROTECT, BROWNOUT, PUT, NOLVP
#use delay(clock = 20000000)


#include "C:\Users\deli\Documents\Google Talk Received Files\teng\brum\Flexlcd2.c"

//==========================

#define      LED1     PIN_D7
#define      LED2     PIN_D6
#define      LED3     PIN_D5
#define      LED4     PIN_D4

void main(void)
{
       int16 temp_adc,counter1;
       int temp, inout_counter=0,PIR1,PIR2,in,out;


        setup_adc(ADC_CLOCK_DIV_8);
        setup_adc_ports(PIN_A1);
        set_adc_channel(1); //read analog input from channel 1


        lcd_init();

         lcd_putc("\fTemperature:\n");

          while(1)


          {
	        PIR1=0;
          PIR2=0;
          in=0;
          out=0;
            temp_adc = read_adc();
            temp = 5.00*temp_adc*100.00/1023.00;
            lcd_gotoxy(1,2);
            printf(lcd_putc,"%d",temp);

          {//?


          PIR1 = input(PIN_B6);
          PIR2 = input(PIN_B7);

	  if(PIR1==1)
          {
            for(counter1=2000;counter1>0;counter1--)
            {
               PIR2 = input(PIN_B7);
               delay_ms(1);
               if(PIR2==1)
               in=1;
            }
            if(in==1)
            inout_counter++;
          }

          else if(PIR2==1)
          {
            for(counter1=2000;counter1>0;counter1--)
            {
               PIR1 = input(PIN_B6);
               delay_ms(1);
               if(PIR1==1)
               out=1;
            }
            if(out==1)
            inout_counter--;
          }

          if(inout_counter>0)
          {
            if((temp<20))
            {
            //delay_ms (500);
            output_high(LED1);
            }
            else
            {
            output_low(LED1);
            }

            if ((temp>= 20) && (temp_adc <30))
            {
            output_high(LED2);

            }
            else
            {
            output_low(LED2);
            }

            if ((temp_adc >= 30))
            {
            output_high(LED3);

            }
            else
            {

            output_low(LED3);
            }
         }
         else

         output_high(PIN_D4);
        }
        }

}